'Noise' in brain's signaling affects motor performance
Sep 24, 2005 - 3:18:00 PM
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"Neuroscientists are interested in what limits virtuosity. Our finding is significant because it demonstrates that errors in what is seen can have a bigger impact on motor performance than errors in controlling muscles"
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By University of California - San Francisco,
[RxPG] A UCSF study has revealed new information about how the brain directs the body to make movements. The key factor is "noise" in the brain's signaling, and it helps explain why all movement is not carried out with the same level of precision.
Understanding where noise arises in the brain has implications for advancing research in neuromotor control and in developing therapies for disorders where control is impaired, such as Parkinson's disease.
Study co-investigators are Leslie C. Osborne, PhD, a postdoctoral fellow at UCSF, and William Bialek, PhD, professor of physics at Princeton University.
The study findings, reported in the September 15 issue of the journal Nature, are part of ongoing research by Lisberger and colleagues on the neural mechanisms that allow the brain to learn and maintain skills and behavior. These basic functions are carried out through the coordination of different nerve cells within the brain's neural circuits.
"To make a movement, the brain takes the electrical activity of many neurons and combines them to make muscle contractions," Lisberger explains. "But the movements aren't always perfect. If there were no noise in the neuromotor system, a player would be able to perform the same motion over and over and never miss a shot. But noise prevents even the best players in the NBA from having perfect foul-shooting percentages, he says.
"Neuroscientists are interested in what limits virtuosity. "By studying how the brain reduces noise, we can learn more about how it processes sensory inputs, makes decisions and executes them. Understanding how noise is reduced to very precise commands helps us understand how those commands are created," adds Lisberger, who also is a Howard Hughes Medical Institute investigator and a UCSF professor of physiology.
In the study, the research team focused on a movement that all primates, including humans, are very skilled at: an eye movement known as "smooth pursuit" that allows the eyes to track a moving target.
In a series of exercises with rhesus monkeys in which the animals would fixate on and track visual targets, the researchers measured neural activity and smooth pursuit eye movements. From this data, the team analyzed the difference between how accurately the animals actually tracked a moving object and how accurately the brain perceived the trajectory.
Findings showed that both the smooth pursuit system and the brain's perceptual system were nearly equal.
The differences that exist are likely caused by the separate parts of the brain that are responsible for the separate processes."
Making precise movements in the face of this noise is a challenge. This study gives us new insights into how the brain works to do that."
Publication:
September 15 issue of the journal Nature
On the web:
www.ucsf.edu 
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Additional information about the news article
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The research was supported by grants from the National Institutes of Health and the Howard Hughes Medical Institute.
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